Advanced Cellular Dynamics And Membrane Physiology Assessment Practice Tests

Question 1

A researcher measures the membrane fluidity of a synthetic lipid bilayer at two temperatures, $T_1 = 290	ext{ K}$ and $T_2 = 310	ext{ K}$. If the addition of cholesterol reduces the fluidity change by a factor of $k = 0.4$, calculate the effective fluidity shift $\Delta F$ if the baseline shift without cholesterol is $1.5$ units. The formula is $\Delta F = (1 - k) 	imes 1.5$.

Accepted Answer

0.9 units

Answer

0.6 units

Answer

1.2 units

Answer

2.1 units

Question 2

A transmembrane protein spans a bilayer of thickness $d = 5	ext{ nm}$. If the protein is composed of an alpha-helix with $3.6$ residues per turn and a rise of $0.15	ext{ nm}$ per residue, calculate the minimum number of amino acid residues $n$ required to span the membrane.

Accepted Answer

34

Question 3

Which of the following scenarios would lead to a decrease in membrane fluidity? Select all that apply.

Answer

Increasing the concentration of cholesterol at high temperatures

Answer

Increasing the proportion of saturated fatty acid tails in the phospholipids

Answer

Increasing the temperature of the system

Answer

Incorporating more unsaturated fatty acids into the bilayer

Question 4

If a peripheral protein is attached to the cytoplasmic side of the membrane via a spectrin meshwork, its dissociation constant $K_d$ will increase if the structural integrity of the spectrin network is compromised.

Accepted Answer

True

Answer

False

Question 5

The glycocalyx contains GAGs that create a hydrated gel. If the osmotic pressure $\Pi$ exerted by a GAG layer is modeled by $\Pi = cRT$, where $c$ is the concentration of fixed negative charges, $R$ is the gas constant, and $T$ is temperature, what happens to the water influx if $c$ doubles?

Accepted Answer

The osmotic pressure doubles, increasing water influx.

Answer

The osmotic pressure remains constant.

Answer

The osmotic pressure is halved, decreasing water influx.

Answer

The osmotic pressure increases by a factor of 4.

Question 6

A cell surface has a density of $N = 500$ glycoproteins per $\mu	ext{m}^2$. If the total surface area of the cell is $A = 400	ext{ }\mu	ext{m}^2$, calculate the total number of glycoproteins $T$ on the cell surface.

Accepted Answer

200000

Question 7

Integral proteins can be removed from the lipid bilayer using only high-salt buffers that disrupt electrostatic interactions.

Accepted Answer

False

Answer

True

Question 8

A cell is placed in a solution where the concentration of a non-permeable solute is $C_{out} = 0.3	ext{ Osm/L}$ and the intracellular concentration is $C_{in} = 0.15	ext{ Osm/L}$. Given the osmotic pressure formula $\Pi = iCRT$ where $R = 0.0821	ext{ L} \cdot 	ext{atm}/(	ext{mol} \cdot 	ext{K})$ and $T = 310	ext{ K}$, calculate the difference in osmotic pressure $\Delta\Pi$ between the outside and inside of the cell.

Accepted Answer

3.82 atm

Answer

1.91 atm

Answer

7.64 atm

Answer

0.15 atm

Question 9

The Na⁺/K⁺ pump moves 3 Na⁺ ions out of the cell and 2 K⁺ ions into the cell per ATP hydrolyzed. If a cell hydrolyzes $1.2 	imes 10^6$ ATP molecules per second, determine the net rate of charge movement across the membrane in elementary charges per second ($e^-/s$).

Accepted Answer

1.2 x 10^6 e^-/s

Question 10

In a secondary active transport system, the energy for moving a solute $S$ against its gradient is provided by the electrochemical gradient of Na⁺. If the Gibbs free energy change for Na⁺ moving down its gradient is $\Delta G_{Na} = -15	ext{ kJ/mol}$, what is the maximum concentration ratio $\frac{[S]_{in}}{[S]_{out}}$ that can be achieved for a neutral solute $S$ if the process is coupled 1:1?

Accepted Answer

403.4

Answer

2.7

Answer

15.0

Answer

1024.0

Question 11

If the permeability coefficient of a membrane for a substance is $P = 1.5 	imes 10^{-6}	ext{ cm/s}$ and the surface area is $A = 200	ext{ cm}^2$, the flux $J$ when the concentration gradient $\Delta C = 0.05	ext{ mmol/cm}^3$ is $1.5 	imes 10^{-8}	ext{ mmol/s}$.

Accepted Answer

True

Answer

False

Question 12

Which of the following scenarios describe processes that require direct or indirect metabolic energy expenditure?

Answer

The Na⁺/glucose symporter in the intestinal epithelium

Answer

The uptake of LDL cholesterol via clathrin-coated vesicles

Answer

The maintenance of the resting membrane potential by the Na⁺/K⁺ ATPase

Answer

The diffusion of $O_2$ across the alveolar membrane

Question 13

A vesicle with a radius $r = 0.1	ext{ }\mu	ext{m}$ is formed during endocytosis. Assuming the vesicle is a perfect sphere, calculate its surface area $A$ in $\mu	ext{m}^2$ ($A = 4\pi r^2$).

Accepted Answer

0.1257

Question 14

A signaling molecule is released by a cell and binds to receptors on the same cell to trigger a response. If the concentration of the signaling molecule $C(t)$ follows the decay function $C(t) = C_0 e^{-kt}$, where $C_0 = 10$ nM and $k = 0.2$ min$^{-1}$, calculate the concentration after $t = 5$ minutes.

Accepted Answer

3.68 nM

Answer

2.00 nM

Answer

5.00 nM

Answer

7.36 nM

Question 15

Which of the following cellular processes directly involve actin filaments?

Answer

Muscle contraction

Answer

Formation of microvilli

Answer

Cytokinesis

Answer

Formation of the mitotic spindle

Question 16

A motor protein moves a vesicle along a microtubule. If the protein moves at a constant velocity $v = 800$ nm/s, calculate the time $t$ in seconds required to travel a distance $d = 12$ $\mu$m.

Accepted Answer

15

Question 17

If a motor protein is identified as dynein, it will transport cargo toward the plus (+) end of the microtubule.

Accepted Answer

False

Answer

True

Question 18

In a signaling pathway, the signal amplification factor $A$ is defined by the ratio of output molecules $N_{out}$ to input molecules $N_{in}$. If one hormone molecule triggers the activation of 100 secondary messengers, and each secondary messenger activates 50 enzymes, calculate the total amplification $A$.

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Question 19

A cell requires a structural component to resist tensile forces. Given that the tensile strength $\sigma$ is defined as $\sigma = \frac{F}{A}$, where $F$ is the force and $A$ is the cross-sectional area, which specific cytoskeletal component is primarily responsible for this mechanical resistance?

Accepted Answer

Intermediate filaments

Question 20

Consider a microtubule as a cylinder with length $L = 25$ $\mu$m and radius $r = 12.5$ nm. Calculate the volume $V$ of the microtubule using the formula $V = \pi r^2 L$.

Accepted Answer

Option A

Answer

Option B

Answer

Option C

Answer

Option D

Advanced Cellular Dynamics And Membrane Physiology Assessment Practice Tests

Practice Tests

Advanced Cellular Dynamics and Membrane Physiology Assessment

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